12 Understanding What's Supported for MySQL

This chapter contains information on database and table features supported by Oracle GoldenGate.

Topics:

• Character Sets in MySQL
  
• Supported MySQL Data Types
  
• Non-Supported MySQL Data Types
  
• Supported Objects and Operations for MySQL
  
• Non-Supported Objects and Operations
  
• System Schemas
  

Character Sets in MySQL

MySQL provides a facility that allows users to specify different character sets at different levels.

Level	Example
Database	create database test charset utf8;
Table	create table test( id int, name char(100)) charset utf8;
Column	create table test ( id int, name1 char(100) charset gbk, name2 char(100) charset utf8));

Limitations of Support

• When you specify the character set of your database as utf8mb4/utf8, the default collation is utf8mb4_unicode_ci/utf8_general_ci. If you specify collation_server=utf8mb4_bin, the database interprets the data as binary. For example, specifying the CHAR column length as four means that the byte length returned is 16 (for utf8mb4) though when you try to insert data more than four bytes the target database warns that the data is too long. This is the limitation of database so Oracle GoldenGate does not support binary collation. To overcome this issue, specify collation_server=utf8mb4_bin when the character set is utf8mb4 and collation_server=utf8_bin for utf8.

• The following character sets are not supported:

  • armscii8
  • keybcs2
  • utf16le
  • geostd8

Supported MySQL Data Types

MySQL supports the following data types:

• CHAR

• VARCHAR

• INT

• TINYINT

• SMALL INT

• MEDIUM INT

• BIG INT

• DECIMAL

• FLOAT

• DOUBLE

• DATE

• TIME

• YEAR

• DATETIME

• TIMESTAMP

• BINARY

• VARBINARY

• TEXT

• TINYTEXT

• MEDIUMTEXT

• LONGTEXT

• BLOB

• TINYBLOB

• MEDIUMBLOB

• LONGBLOB

• ENUM

• BIT(M)

• Limitations and Clarifications
  

Limitations and Clarifications

When running Oracle GoldenGate for MySQL, be aware of the following:

• Functional indexes are not supported for Capture or Delivery.

• Oracle GoldenGate does not support BLOB or TEXT types when used as a primary key.

• Oracle GoldenGate supports UTF8 and UCS2 character sets. UTF8 data is converted to UTF16 by Oracle GoldenGate before writing it to the trail.

• UTF32 is not supported by Oracle GoldenGate.

• Oracle GoldenGate supports a TIME type range from 00:00:00 to 23:59:59.

• Oracle GoldenGate supports timestamp data from 0001/01/03:00:00:00 to 9999/12/31:23:59:59. If a timestamp is converted from GMT to local time, these limits also apply to the resulting timestamp. Depending on the time zone, conversion may add or subtract hours, which can cause the timestamp to exceed the lower or upper supported limit.

• When the time zone of the Oracle GoldenGate installation server does not match the time zone of the source database server, then the TIMESTAMP data sent to the target database will differ from the source database.

  For Classic Architecture, create a session variable for Oracle GoldenGate, called TZ, and set it equal to the time zone value of the database.

• Oracle GoldenGate does not support negative dates.

• The support of range and precision for floating-point numbers depends on the host machine. In general, the precision is accurate to 16 significant digits, but you should review the database documentation to determine the expected approximations. Oracle GoldenGate rounds or truncates values that exceed the supported precision.

• When you use ENUM type in non-strict sql_mode, the non-strict sql_mode does not prevent you from entering an invalid ENUM value and an error will be returned. To avoid this situation, do one of the following:

  • Use sql_mode as STRICT and restart Extract. This prevents users from entering invalid values for any of the data types. An IE user can only enter valid values for those data types.

  • Continue using non-strict sql_mode, but do not use ENUM data types.

  • Continue using non-strict sql_mode and use ENUM data types with valid values in the database. If you specify invalid values, the database will silently accept them and Extract will abend.

• To preserve transaction boundaries for a MySQL target, create or alter the target tables to the InnoDB transactional database engine instead of the MyISAM engine. MyISAM will cause Replicat records to be applied as they are received, which does not guarantee transaction integrity even with auto-commit turned off. You cannot roll back a transaction with MyISAM.

• Extraction and replication from and to views is not supported.

• Transactions applied by the slave are logged into the relay logs and not into the slave's binlog. If you want a slave to write transactions the binlog that it receives from the master , you need to start the replication slave with the log slave-updates option as 1 in my.cnf. This is in addition to the other binary logging parameters. After the master's transactions are in the slave's binlog, you can then setup a regular capture on the slave to capture and process the slave's binlog.

Non-Supported MySQL Data Types

Oracle GoldenGate for MySQL does not support the following data types:

All spatial types (Geometry and so on), JSON, SET, XML

Note:

Extract abends if it is configured to capture from tables that contain any of the unsupported data types, so ensure that Extract is not configured to capture from tables containing columns of unsupported data types.

Supported Objects and Operations for MySQL

Oracle GoldenGate for MySQL supports the following objects and operations:

• Oracle GoldenGate supports the following DML operations on source and target database transactional tables:

  • Insert operation

  • Update operation (compressed included)

  • Delete operation (compressed included)

  • Truncate operation

• Oracle GoldenGate supports the extraction and replication of DDL (data definition language) operations.

• Oracle GoldenGate supports transactional tables up to the full row size and maximum number of columns that are supported by MySQL and the database storage engine that is being used. InnoDB supports up to 1017 columns.

• Oracle GoldenGate supports the AUTO_INCREMENT column attribute. The increment value is captured from the binary log by Extract and applied to the target table in a Replicat insert operation.

• Oracle GoldenGate can operate concurrently with MySQL native replication.

• Oracle GoldenGate supports the DYNSQL feature for MySQL.

  Note:

  XA transactions are not supported for capture and any XA transactions logged in binlog cause Extract to abend. So, you must not use XA transactions against a database that Extract is configured to capture.

  If XA transactions are being used for databases that are not configured for Oracle GoldenGate capture, then exclude those databases from logging into MySQL binary logs by using the parameter binlog-ignore-db in the MySQL server configuration file.

  Limitations on Automatic Heartbeat Table support are as follows:

  • Ensure that the database in which the heartbeat table is to be created already exists to avoid errors when adding the heartbeat table.

  • In the heartbeat history lag view, the information in fields like heartbeat_received_ts, incoming_heartbeat_age, and outgoing_heartbeat_age are shown with respect to the system time. You should ensure that the operating system time is setup with the correct and current time zone information.

Non-Supported Objects and Operations

Oracle GoldenGate for MySQL does not support the following objects and operations:

• Invisible columns

• The Oracle GoldenGate BATCHSQL feature.

• Array fetching during initial load.

• The following character sets are not supported:

  • ULIB_CS_ARMSCII8, /* American National 166-9 */
  • ULIB_CS_GEOSTD8, /* Geogian Standard */
  • ULIB_CS_KEYBCS2, /* Kemennicky MS-DOS

• Capturing NLS LOB data using the FETCHMOCOLS and FETCHMODCOLEXCEPT TABLE options is not supported when DDL is enabled.

• Renaming tables.

• DDL statements inside stored procedures is not supported.

• When the time zone of the Oracle GoldenGate installation server does not match the time zone of the source database server, then the TIMESTAMP data sent to the target database will differ from the source database. For Oracle GoldenGate Microservices installations, regardless of the time zones being the same, Extract will resolve the time zone to UTC. Determine the source database time zone by running the following query:

  select @@system_time_zone; 

  This will return a time zone value, such as PDT.

  Create a session variable for Oracle GoldenGate, called TZ, and set it equal to the time zone value of the database.

• Extraction and replication from and to views is not supported.

• Transactions applied by the slave are logged into the relay logs and not into the slave's binlog. If you want a slave to write transactions the binlog that it receives from the master , you need to start the replication slave with the log slave-updates option as 1 in my.cnf. This is in addition to the other binary logging parameters. After the master's transactions are in the slave's binlog, you can then setup a regular capture on the slave to capture and process the slave's binlog.

System Schemas

The following schemas or objects are not automatically replicated by Oracle GoldenGate unless they are explicitly specified without a wildcard.

• 'information_schema'

• 'performance_schema'

• 'mysql'

• 'sys'